Add namespace

[danielabutano]

I have added a new field "namespace". Please test:

• [x] the namespace is mandatory and unique.
• [x] Once assigned it can NOT be modified!!
• [x] The namespace is used to provide the actionable identifier for the mine instance
  The identifier will be: registry.intermine.org/{namespace}The identifiers is actionable, so if you put registry.intermine.org/flymine in the address bar of your browser, you will be redirected to the URL set in the flymine instance
• [x] I have updated the existing webservice registry.intermine.org/service/instances/{namespace} to accept also the namespace (in addition to the ID and the name).

Please suggest :)

• [x] how to set the status code when redirect this https://github.com/danielabutano/intermine-registry/blob/add-namespace/routes/index.js#L284 does not work
• [ ] how to apply reg expr to the namespace. this https://github.com/danielabutano/intermine-registry/blob/add-namespace/routes/instances.js#L167 does not work. Also tried pattern in instance_validate_schema.js without success

[yochannah]

@danielabutano I've checked the bits that add and update:

When I try to add a namespace (update an instance) or add a new instance, I'm getting a few errors - the update form is only half populated and the server process quits when I try to save an instance.

I think mostly we need to check for null values in certain places. The error is happening in a couple of different places, too. Would you mind if I refactored a little?

I still need to check the other bits of this PR so I may have more comments.

[danielabutano]

Thanks @yochannah. Please go ahead